This story about what i've to do to upgrade my old ClamAV version.

Currently, I'm working with ClamAV 0.92.1 in my slackware 12.0.

Upgrading to 0.94.2

1. Download the ClamAV latest stable release at http://www.clamav.net/download/sources/

2. Extract

 root@linux# tar -zxvf clamav-0.94.2.tar.gz

3. Stop any clamav running services

 root@linux#killall -9 clamd

4. Backup existing configuration and signature database files

5. Uninstall the old version

 root@linux# cd clamav-0.94.2
 root@linux# ./configure
 root@linux# make uninstall

6. Make sure  that i haven't got old libraries lying around my filesystem

 root@linux# ldd `which freshclam`
 root@linux# whereis freshclam
 root@linux# whereis clamscan

7. If nothing left, let's strating to configure and install the latest ClamAV

 root@linux# ./configure --sysconfdir=/etc --with-dbdir=/var/lib/clamav
 root@linux# make && make install

7. Restore backup configuration and signature database files

8. Check definitions are up to date.

 root@linux# freshclam

9. Finish

FAQ :

Q : I see an error about loading shared libraries when starting "freshclam" after upgrading. 

libclamav.so.5: cannot open shared object file: No such file or directory

A : Try to run as root the following command and run your freshclam again.

 root@linux# ldconfig

source :

http://wiki.clamav.net/Main/UninstallClamAV
https://wiki.clamav.net/Main/InstallFromSource